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Bevel Pinions.


In Fig. 72/5 we have the core box required for the arms of a
machine-moulded spur wheel; its description will serve also for
bevel wheels. A represents the casting to be obtained, having
six arms, and the box at B is so designed as to core out a space of
one-sixth of that within the wheel rim. The box being in the

foundry is placed on a true table a, and after filling with loam, is
smoothed off with straight-edged batten at b. Six of these cores
being dried and blackwashed, a pattern for the boss of the wheel is
now necessary to complete the mould.

Small Bevel Pinions require the patience of the pattern
maker. Referring to Fig. 73, which is the section of a bevel
pinion, it will be seen that the teeth vary in size from A to B,
and must, therefore, be entirely gouged out by hand. The body
of the pattern is carefully turned as at c c, while blocks D, for
the teeth, are planted on in hard wood and again turned, as in
the last example. The section of the tooth now being set out by
compass or template at A and B, the teeth have to be cut out and
finished by hand. The teeth at B are made correctly lineable
with those at A by means of the wooden spindle K, carrying a
straight edge F so cut as to be always truly radial when moved
round the surface A B.